Apparatus for roasting vegetable materials



July 7, 1953 w. s. scuu. 2ND., Ei'AL 2,644,681

APPARATUS FOR ROASTING VEGETABLE MATERIALS Original Filed April 8, 1947 3 Sheets-Sheet 1 ATTORNEYS July 7, 1953 7 w. s. scum. 2ND. ETAL I APPARATUS FOR ROASTING VEGETABLE MATERIALS Original Filed April 8. 1947 3 Sheets-Sheet 2 Ml TORNEY$ y 3 w. s. scum, awn, run 2,644,681

APPARATUS FOR ROASTING VEGETABLE MATERIALS Original Filed April 8, 1947 s Sheds-Sheet s l INEEORIS II ATTORNEY-S Patented July 7, 1953 ,UNITED', sTAres PATENT OFFICE 2,644,681 a ArPAa UsjFoaRoAsTIN VEGETABLE William s; Scull MATERIALS 2nd, Bryn Mawr, and George A.

Fisher, Selinsgrove; Pa., a'ssignors,iby mesne as- 1. signments; to. J abez' Burns &: Sons, In,c.,;,a,y ,cor

f r nal: ap cation A il, @1 1 Se Divided and this Our inventionhimtodotmithagorocess and 31 paratus for:roasting;avegetab-lewmaterialss suchas cofiee; nuts, beansrand: the like,';and is .particularlynusefullfor roastingzcoffeeaxthis commodity is one of the mostad'iflicultdzo roast successfully withuniform highiquality;i .The processiiis the s ubject of- Serial N 0. 740,156, filed Apri1"8;- .'194'7; IIOWJQQGBIlt No: 2,581148sthriroastingi apparatus ibeing:the subject of the present divisional aDp1ication; *sIn the description ofirourxinvention, wehave therefore referredi specifically-toathei roastingzof coflfee. It will be understood, however, that the by means of which the coffe'e'maybe' roasted in a conditioned atmosphereand with control of'the processes in all stages'which can be so 'c'arefully adjusted'that'the desired'uniforrn-high quality results will beassuredti Fundamentally; there ere' itwc stages inthe roasting of" coffee: first, the v dehydratiom sta'ge and, second; the" actual roasting or development stage u. t. H 'I'he..green coifee beans normally -containfup to about 20% moisture. In 'the dehydrationf'stage, the heating f the beans drives oi? thegreater Part:- of the moisture "andl-vcerta'in' "chemical changes take place. In the roa'stingor'develop- 1 ment stage the" dehydrated -beans=undergo fur-.

ther chemical changes and it--- 'is-"we1l known in the art that the addition of the-last- 10%' of" the heat must be carefully'controlled in order to obtain'unif'orm' high quality flavor.

:Asa matter of fact, the matter of a few secodds at the end of the roasting stage will produce such ainarkedefiect on the quality nf the c-ofiee that We believe it preferable to regard-the final heat ihputperiod' as a separatestage'in the cof- I fee roasting process and,for that reason, we treat the {roasting asfa three stage p'rc'ic'ess'. I We, can

- the first the dehydration stagei the "second a the deyloliment stage; fafidthe'thirdthe fegplcsire and coloring stage} '4 Claims. (01. 263-34) ur application v lowed-t9, com t -t n ed" application May -5,

t .Itiis 4 known that; =the.:co1oring stageiis critica inproducing coffee of good quality andsuniform; 'ity offlavo'r and itii zkn'own thatiin any partie lar time-temperature roasting-cycle with a given grade of :coffee' the: production of cofieezof'a, uni: form .color-resu-lts in lthegproductionof q fiee which will-yield-uniform cup quality? During the dehydration and development;stages,::-it ;.estimated from experiment athat-eabout :of .ztrhe heat'i required maybe added to the coffeeland still not materially darkenltheecoloria It: .is i.the addition of-Jthe 1ast--.1-0;% ;0f th ezheat which substantiallyflafiects -'CO1OI ing-i"a;nd: th1IS 'theultimate fiavorr'ofthe coffee.. a s w -Ac'curate control: ofi theicoloring stage he roasting process is therefore one;of thelimporta-nt factors in any zsuccessfuliroastingip'rocess; and it i's' one of the objects of our invention to-lprovide apbaratus1wherein this accuratescontrolsecured-.1, Q1 Ii'ij I *In the dehydration. stage? the heating -of he beans drives ofl the greater part of :the moisture and bertain 'chemical. changesitake place. :5 a; We' believe that chemical changes which take place in'the' dehydration zonetare' of greater-rim"- ;p'ortanc v than has hitherto beenrec'ognized and We'haire discovered that -a hi, .3:h and rapid heat input in the dehydration zone 'produces 'a cofiee the presence orabsence of n ioistu a will-have a nce is tlf atmos here tedfW a c i1 improved fiavoiywill bes u d if h coffee is roasteagunder conditions; .(1); i which a irl a the gaseous products of combustion nai e notalt new .n 21):, therr a i v 42arifl d-sou in e o-zetm whe e consistingiof the gases evolved-, duringthe'; roasting processv Q It: is, therefore;v a iurtherrobiecti-zof our invention-"to provide roasting apparatus in which 'sucn cbnditiozis prevail; z ithi's e nneetiofi it should be state that-r11: is not necessary br'practica1 to jeiiclud of the arm the roaster is-a msu ama gm will come in with' thefcofiee beans? a w yemhe amount emircornifigidwiththe beat-swimmer be g reat in size very slightly, Whereas in'rapid roasting 1 f,

the increase in size or development is such that the coffee will practically double-involumea This pe ureb er a is because with rapid roasting inthe final stages Y the beans will explode or break open due tethe internal pressure, Whereas with the slower roasting this final explosive and it has been found that-the quality of coffee which is fully developed by a rapid roast is much superior to that which has not substantiallyincreased in volume.

Our improved process, be" car ried' out indifferent ways, but We have found thatin'any case in thefirst stage'of the roasting (iZ'e'. the dehydration stage); it is desirable that the coffee be subjected to ta high temperature first and generate steam in order to exclude air from the roaster and provide conditioned atmosphere in which other steps of the process can be 'carri edout and, second, to acceleratethe'che'mical reactions which take place in the presence of the moisture in'thebeans:

However, in the development and roasting stages, the time-temperaturerelationship can-be varied in order to provide short time, high temperature condition or longer time, lower temperature conditionsn 2 V For example; the coffee can firstlbe subjected for a predetermined period of time to a high ten'lperaturefor reasons aboveset forth. The coffee can then be subjected to a lower temperature' for substantially the same period'of time in order to develop it andfinally subjected to a lower temperature for'substanti-ally the same period of time in order to color or'finally develop the beans. However, if P desired, the beans canbecompletely roasted in' three stages where the temperature is maintained substantially the same in each stage. If this is done, however, it is necessary that the time factor be changed so that the'beans are subjected to the heat in the second stage for asubstantially less period of time than-in the first and are subjected tothe heat in the third stage for much-less time than in the process first described. Securing the proper heat input in'each-stage ofthe roasting is the controlling'factor. a

In general,- we preferto. carry out our im: proved process in a roaster in which the coffee is heated in each stage of the process for the same lengthof time but :at progressively lower temperatures in each stage. I I

In the coffee roasting are; another problem which is met is in roasting blends of coffee; This is due to the different moisture content of the beans of different blends and't'o differences in si'ze'and other characteristics. It will be understood that when beans of different moisture content, size, etc., are roasted together, especially in a continuous process, the total .heat input requirement will vary for the different coffees, and, unless .a provision is made for overcoming the difficulty, beans of one coffee willbe' roasted to a different degree than beans of another coffee- Sometimes each,coffee is .roasted separately and the blending done after the roasting.

stage-may-not be reached in certain stages, can

to substantially dehydrate it 4 However, there are certain advantages in roasting a blend after the various coffees comprising the blend have been mixed together and in such caseit has been the'practice; 'where a continuous process'is to-be usedjto first condition the beans in order to secure uniformity of the mois- ;;ture content in the various coffees to be roasted. This co'nditioning is accomplished either by storfingthe blended coffee in silos, generally for several weeks, or by maintaining it at a low temperiod of time. In many commercial" roasters using the batch process, good results are" secured in roasting blends without conditioning, apparently because the cofiee is treated insuch large masses and in such close contact th'at the 'moisture of the beans appears to equalize during the roasting process and there is, therefore, no need for conditioning. So far as'we' are aware, however, it has heretofore been impossible to roast blends in a continuous process without preconditioningthe coffee.

It is-a f-urtherobjectof our invention to provide an improved apparatus for continuous roasting of coffee in which it is possibleto roast ablend without-preconditioning. c

In the accompanying-drawings, we'haveillu's 'tratedtwo forms of apparatus for-carrying out our improved process.

Figure-1 is aside elevation of one form of our improved roaster; I

Figure 2 11s a plan viewofthe roaster illustrated-in Figure 1-, taken on the line 2-2 'of- Figure 1;.

Figure 3 is an enlarged sectional elevation of the'first and a portion ofthe second of the roasting. compartments of the roaster illustratedin Figure 2;

- Figure 4 isa section takenzalong the line 4-'4 ofFigure-l; and r 1 Figure 5 is a diagrammatic illustration of the control mechanism for' the fuel supply to the burners forthe various zones of'the roaster.

Referringnow to Figure 1, the roaster is supportedin the frame, 8 which consistsof upright channel members 9 which support the horizontal framemembers IO'and ll.

The oven l2; comprises a sheet metal casing 13 which islined with refractory insulation [4 which can conveniently take the form of magnesium blocks. The; oven-is divided lengthwise into three roasting compartments-A, -B and C-by refractory partitions: I5 and is .closed at the' end by refractory walls l6; ,Elhe roasting tube- H extends fromone end ofthe oven to the other and at either end isprovided with a head [8 from whichthe tube asa' whole is supported. The: head'- 18 is mounted for rotary. movementon trunnions I9' and the head at one endgis-driven by means of ring gear 20 which is drivenby the gear- 2 I carried by drive shaft22 which is driven ,by a motor (not shown) fromqa convenient loca-,

tion on-the floor orin the frame. t Coffee is fed to theinletend of the hopper 23. From this hopper the coffee flows through the spout 2 to-endless belt '25 which is driven by means of; motor 26 through appropriate belts and pulleys. From the endless belt 25, ooffeeis delivered into a feed spout 21. To the end of the spout, adjacent the tube, there. iswelded a flange orring 2 8 which is the same diameteras the tube. The purpose of this flange is to close the end of the tube. The flange is held against the end of the tube by means of springs 29 which are supported by brackets 30. Between'the ring and the end ofthe tube there the tube from 7: of the: tubei. the helix: 58 and the longitudinal strips 51,.and when in contact with these parts through the tube, it is heated inthree stages or zones corresponding-to the compartments A, B and Cofthe-oven, and it will-further be observed that the design of the helix is such that the coffee will move through each zone at the same rate-of speed. In other words, the coffee is exposed to the heat in each zone for the same length of time.

In compartment A, the tubeis heated at a term peratureranging between 600 and 1200", in the final zone to a temperatureranging between 300 and 650, and in the middle zone to a temperature substantially midway of the temperature to which the first andthird zones are heated. The roasting time can vary between -'70 seconds and six minutes dependingon the temperature of the tube and rate of feed'of coffee to the tube.

It will be understood, of course, that the roaster can be used to roast cofiee in the conventional. roasting time ofv about eighteen minutes with improved results due to the conditioned atmosphere inwhich the roasting takes place. However, the rapid roasting of the coffee which is possible with our roaster is much more preferable. It isto be observed that the heating of the beans in the tube is done indirectly, that is by contact with the wall of the tube, the helix and longitudinal strip and also by radiation from those elements. Products of combustion or flames do not come in contact with the coffee beans and the steam and other gases evolved from the coffee during the process prevent the entrance of any air. The process may therefore be said to be carried out in an atmosphere consisting substantially solely of the gases evolved during the process. As was pointed out above, it ls-probable that a small amount of air enters the tube with the beans but this amount is so insignificant that for practical purposes it can be disregarded.

By varying the speed atwhich the tube is rotated, the speed at which the coffee is moved throughout the tube can be varied and, therefore, by controlling the speed of rotation of'the tube and the temperature of the different compartments, a very accurate control of each stage of the roasting process is secured. In general, in

order to roast rapidly, we prefer to maintain the temperature of the tube in the first zone at about 1000F.; in the second zone at about 800 F.; and in the third zone at about 600 F., with a total roastingtime of three and one-half minutes, the Coffee therefore being exposed to the heat in each zone for approximately one minute and ten seconds.

It is quite possible, however, to secure excellent results within the ranges of temperature which I set forth previously and with certain coffees it may be found that other'temperature-time conditions within the ranges given will be desirable.

In the roasting process, due to the high heat input into the coffee in compartment A, the coffee is rapidly dehydrated and steam is generated. The steam and other gases which are generated 8. in the first zo'rie of the apparatus are drawn through the tube toward the exit end-by means of the exhaust fan-35. It is-to be observed, however, that this exhaust'fan is run at a speed sunlcient only to remove gasesgenerated in the process" as they are evolved andthe speed of rotation of the fan should be such that there is a slight positive pressure throughout the length of the tube. This slight positive pressure throughout the tube will prevent the entrance of any air into the tube from either end and it isour general practice in roasting. to soregulate the speed that a slight amountof steam will escape at the inlet 7 end of the'tube, thus preventing any air being introduced into the tube excepting that which is entrained withthe stream of beans or within the beans themselves. In the second or developmentzonethe coffee undergoes further chemical changes which result in converting the starches, proteins and other constituents in the coffee to the materials responsible for the coffee flavor, body and aroma. Volatiles are also liberated fromthe coffee in this zone and form part of the atmosphere in which the roasting in the second and third zone is carriedout. It is desirable, however,

that the liberation ofthe volatiles from the coffee be held at a minimum and this is one of the reasons why we prefer to carry out the roasting in the second zone at a temperature as low as possiblefor the time allowed.

On leaving the development zone, the coffee next passes to the coloring zone where the temperature is substantially lower than in the development zone and in this zone the coffee is given its final color. .It will be borne in mind that inboth the development and coloring zones the roasting of the coffee is carriedout in the presence of the steam'andother gases evolved from the beans in the dehydration zone. In the de-' velopment and coloring zones, gases evolved from the roasting will also be present. Just what effect the presence of these gases has we are unable to state; however, it is our belief that the presence of these gases plays a great part in the improved -the tube, the mass of beans at any particular point in the tube will be so great that all of the beans do not come into contact with the tube walls or at any rate would contact the tube walls only occasionally. Uneven roasting of the beans naturally results. We'have found that it is desirable to feed-the beans atsuch a rate that substantially allof-the beans which are dropped to the bottom of the tube: will be picked up by the longitudinal strips as they move upwardly from the bottom of the path of revolution. In

other. words, the mass of beans at the bottom of the tube at any particular point isnot su1fi'. ciently great to bury the longitudinal strips and cross-se'ctionally considered the beans occupy a relatively small amount of the space within the tube. Figure 4-- illustrates in general the dis tribution of beans inthe tube; V

"with therate' of feed bein V twenty-six pounds of beansinwthe tube at all times, the variation There would be no'particular lower'limit as tothe amount of beans fed in any particular period of time insofar as the roasting of the beans is concerned; However, from a practical in a roaster having an eighteen foot tubepf-"ten 'inch diameter (the general -proportion of di- .me'nsions of the apparatus illustratedin; the drawings), we have found "itj'p'racticali to roast between 350 and 500 pounds "of coffee per-hour g such thatthere' are istttput "between" 350 and 500 pounds, depending on the speed of rotation of the tube. v

In order to determine the color of the beans,

we have used a colorimeter adapted to distinguish variations of shade between a slightly colored or slightly brown bean to a bean of a very deep brown color, with the mid point of the range being the desired coffee color. The colorimeter is calibrated into ten divisions and we have found that with out improved process and apparatus it is possible to hold the color of the roasted coffee within one-half degree of calibration.- The variation in shade of a half degree of color is almost impossible to distinguish with the human eye and in conventional coffee roasting apparatus even the most expert coffee roast- 1 ers are unable to maintain any such degree of color uniformity due to varying factors which affect the eye in determining color.

In the apparatus above described, it will be observed that the oven is divided into three distinct compartments which are heated to successively lower temperatures from the inlet to the outlet end of the roasting tube. In the arrangement described and illustrated, it is therefore possible to provide three distinct heating zones or stages for the coffee passing through the tube and this is the preferable method of roasting. It will be understood, however, that y it would be possible to increase the number of the compartments so as to provide agreater number of heating zones or the oven could have a single compartment with the tube heated by any means providing a diminishing heat from inlet to outlet end, e. g., by providing a large number of burners at the inlet end with the number of burners decreasing toward the outlet end.

We prefer the use of the three-compartment oven as it provides better control of the heat in each stage of roasting as compared to an uncompartmented oven and, as compared to an oven having a greater number of compartments because three compartments are sufiicient to secure optimum results and the cost of is less.

When employing the apparatus and proceeding as first above described, optimum results are obtained; but we believe that we are the first to provide a single imperforate and substantially closed, elongated, relatively small diametered heating tube through which the beans are adthe oven vanced and successively dehydrated, developedand colored, in a relatively small advancing stream,

- to be limitedfto the employment of videdwith a coffee against the entrance of air 0 cros s-sectionallyv 1 considered, tially solely in the presence of the. vapors and gases ev'olvedfromthe coffee beans, and therefore, in its broadest aspects, our invention isnot a compartmentedoven as hereinbefore'des'cribed.j

We claim:' 1. A coffee roaster comprising an 'ovenhavirig aplurality of successive heating Zonesheatin'g -means to heat said zones to successively lower having airf-tight 1 unvented walls toprevent the passage of any 'air lintothe tubeqand to 'roast the coffeebeans in an temperatures, a; roasting tube atmosphere of gasesevolved during the roasting processes, said walls having at one and the same end of 'the' 'tube' a discharge and exhaust outlet to remove gasesevolved during the roasting process and discharge the roasted coffee beans and at the other end a sealing closure probeaiiinlet tubeadap ted t'o'be sealed, by f'entfering coffee beans to I reduce the entrancebf airto small 'quantities' unaffec'ting the coffee roasting and maintaining it substantially solelyin the presence of the vapors and gases evolved from the coffee beans, means to rotate said tube, and a coffee bean advancing helix within said tube to advance the coffee beans therethrough from the high to the low temperature end when the tube is rotated, and exhaust means connected tothe discharge and exhaust outlet end of said tube including means sealing the coffee discharge against the entrance of air into the tube whereby gases evolved from the coffee during the roasting process may be drawn from the tube. l

2. A coffee roaster comprising an oven having a plurality offsuccessive heating zones, heating means to heat said zones to successively lower temperatures, aroasting tube having air-tight unvented walls to prevent the passage of any air into the tube and to roast the coffee beans in an atmosphere of gases evolved during the roasting processes, said walls having at one and the same end of the tube a discharge and exhaust outlet to remove gases evolved-during the roasting process and discharge the roasted coffee beans and at the other end a sealing closure pro- =coffee roasting and maintaining it substantially solely in the presence of the vapors and gases evolved from the coffee beans, means to agitate the coffee beans and to advance them through said tub-e from the high to the low temperature end thereof, and exhaust means connected to the discharge and exhaust outlet end of said tube including means sealing the coifee discharge into the tube whereby gases evolved from the coffee during the roasting process may be drawn from the tube.

3. A coffee roaster comprising an oven having a plurality of successive heating compartments, heaters for each compartment to heat said com-.

temperatures, a

partments to successively lower roasting tube having air-tight unvented walls to prevent the passage of any air into the tube and to roast the coffee beans in an atmosphere of gases evolved during the roasting processes, said walls having at one and the same end-of the tube a discharge and exhaust outlet to remove gases evolved during the roasting process anddischarge the roasted coffee beans and at the other end; a sealing closure provided with a coffee bean inlet'tube adaptedto be sealed by entering substan- 1.1 coffee beans to reduce: the entrance of airto small quantities unafiecting the coffee roasting and maintaining it substantially solely in the "presence of the vapors and gases evolved from the cofie'e beans, means to rotate said tube and a cofiee bean advancing helix in said tubeto advance the coffee beans therethrough when the tube is rotated, a housing surrounding the discharge and exhaust outlet end of said tube and having a roasted coffee bean discharge and a gas discharge and an exhaust fan connected to said ,gas discharge of said housing adjacent the end of the tube including'means sealing the cofiee discharge against the entrance of air into the tube whereby the gases evolved from the coffee during the roasting process may be'drawn from the tube to the outlet vend thereof.

4. A coffee roaster as set forth in claim 2 wherein said means; to agitate the coffee beans and to advance them through said tube from the high to the low temperature end thereof comprises a helix having its outer edge in con- 12 ct wi hh nn u iace tub ndca p1u= rality of longitudinally extending .bafiies incontact with and spaced circumferentially of the inner surface of the tube;

" W. S'SCULL-ZND.

GEORGE A. FISHER.

Befeeme Ci e? in t e .fi o this a en UNITED STATES PATENTS 

